Domestic sewage biological treatment system and process based on iron driving

Abstract

The invention discloses a domestic sewage biological treatment system and process based on iron driving, and belongs to the field of sewage biological treatment. The treatment device comprises a water inlet tank and two reaction tanks which are sequentially connected through a pipeline, the two reaction tanks are sequentially a dissimilatory iron reduction reaction tank and a Fammox reaction tank, each reaction tank is provided with an iron source feeding port and an effluent weir, the dissimilatory iron reduction reaction tank is filled with sludge with an iron reduction function, and the Fammox reaction tank is filled with sludge with a Fammox function. According to the method, dissimilatory iron reduction, iron autotrophic ammoxidation and iron autotrophic denitrification technologies are coupled, so that organic matters, nitrogen and phosphorus in the sewage are synchronously removed, the treatment cost is low, and the emission of greenhouse gases is reduced.

Description

Technical Field

[0001] The present invention belongs to the field of biological sewage treatment, and relates to a biological sewage treatment system and process based on iron-driven, and specifically relates to a biological sewage treatment system and process of dissimilatory iron reduction, Fe(III) / Fe(II) cycle-driven iron ammonia oxidation (Feammox) coupled with nitrate-type ferrous oxidation (NDFO), and adsorption crystallization phosphorus removal process. Background Art

[0002] The pollution of nitrogen and phosphorus in water bodies is a global problem. At the same time, the excessive discharge of organic matter makes the treatment of black and smelly water bodies one of the contradictions that needs to be solved urgently. At present, the preferred biological treatment process that can be applied to large-scale sewage treatment is the nitrification-denitrification method. The traditional domestic sewage relies on the two-stage method (nitrification-denitrification) to remove nitrogen-containing pollutants in the sewage, and remove organic matter and phosphorus and other pollutants at the same time. However, the nitrification process requires additional aeration, which increases energy consumption, and the denitrification is not thorough due to insufficient carbon sources. The additional introduction of organic matter increases the economic burden. At the same time, it is difficult to take into account deep carbon control and deep denitrification. At the same time, traditional treatment technologies have large greenhouse gas emissions and large amounts of sludge treatment and disposal. Compared with heterotrophic denitrification technology, autotrophic denitrification avoids certain disadvantages. As a new denitrification technology, iron ammonia oxidation (Feammox) uses Fe 3+ Oxidation of NH4 + -N is N2, accompanied by some NO X – -N is generated, and Fe 3+ Reduced to Fe 2+ , while Fe 2+ It can react with NO in sewage X – -N reaction, called nitrate-dependent ferrous oxidation technology (NDFO), is an iron-autotrophic denitrification technology. The coupling of the two can achieve the removal of ammonia nitrogen and nitrate in sewage, while achieving Fe 2+ and Fe 3+ In addition to pollutants such as nitrogen, there are also a lot of organic matter in sewage. Dissimilatory iron reduction is a process that can couple carbon and iron. It reduces Fe by oxidizing organic matter. 3+ , thus forming a series of Fe-containing 2+ Minerals can be used to remove organic matter from sewage by using the dissimilatory iron reduction process. At the same time, iron is widely used in sewage treatment as an efficient phosphorus removal material. Therefore, using iron to remove the three major pollutants in sewage can develop a low-carbon, low-material consumption sewage treatment system.

[0003] Low C / N sewage is everywhere, especially in many remote rural areas, where a large amount of domestic sewage is discharged without treatment. Although sewage treatment capacity is increasing year by year, the rural domestic sewage treatment rate is still at a low level. Domestic sewage is discharged directly or with insufficient treatment, becoming an important source of water pollution in rural areas, bringing huge pressure to the rural ecological environment.

[0004] Unlike urban sewage treatment, the bottleneck of rural domestic sewage treatment lies in the limitation of economic conditions: the traditional two-step denitrification technology requires high-energy aeration and additional organic matter, and brings about problems such as excessive carbon emissions and sludge disposal, so it is not suitable for rural domestic sewage treatment. The treatment of rural domestic sewage should be based on autotrophic biological technology, while considering factors such as cost and operation mode. Therefore, it is urgent to develop low-carbon, low-material consumption pollution reduction, denitrification and phosphorus removal technology for the treatment of rural domestic sewage. Summary of the invention

[0005] In view of the drawbacks of high energy consumption and high cost of existing domestic sewage treatment, the purpose of the present invention is to provide a domestic sewage biological treatment system and process based on iron drive, based on dissimilatory iron reduction, Fe(III) / Fe(II) cycle driven iron ammonia oxidation (Feammox) coupled with nitrate type ferrous oxidation (NDFO) and adsorption crystallization phosphorus removal process, which can achieve efficient removal of organic matter in sewage and fixation of carbon dioxide, autotrophic technology deep denitrification and phosphate adsorption and crystallization, synchronous and efficient removal of pollutants in sewage, with the advantages of easy operation and low cost, and is particularly suitable for rural domestic sewage treatment. The purpose of the present invention is achieved by the following technical solutions.

[0006] The primary aspect of the present invention is to provide a domestic sewage biological treatment system based on iron drive, comprising an inlet tank and two reaction tanks connected in sequence by pipelines, the two reaction tanks are respectively a dissimilatory iron reduction reaction tank and an iron ammonia oxidation reaction tank, both reaction tanks are provided with an iron source addition port, a water inlet and an outlet weir, the dissimilatory iron reduction reaction tank is filled with sludge containing iron-reducing bacteria, and the iron ammonia oxidation reaction tank is filled with sludge having iron ammonia oxidation function.

[0007] Furthermore, the dissimilatory iron reduction reaction tank is provided with an aeration system, and the iron ammonia oxidation reaction tank is provided with a stirring system.

[0008] Furthermore, if the C / N ratio in the effluent of the dissimilatory iron reduction reaction pool is greater than 2, a dissimilatory iron reduction pool is added to create a suitable low C / N ratio environment for the subsequent iron-ammonia oxidation.

[0009] Furthermore, if the effluent NH4 + -N>5 mg / L, add an iron-ammonia oxidation reaction tank to achieve the required removal of ammonia nitrogen.

[0010] Another aspect of the present invention is to provide a biological treatment process for domestic sewage based on iron drive, comprising the following steps: S1: Add sludge with iron reduction function into the dissimilatory iron reduction tank, fill it with iron source, introduce domestic sewage, start the dissimilatory iron reduction process and fully react; S2 fills the sludge with iron ammonia oxidation function into the iron ammonia oxidation reaction tank, adds the iron source, and the effluent from the dissimilatory iron reduction tank enters the iron ammonia oxidation reaction tank. After the iron ammonia oxidation process is started and fully reacted, the treated domestic sewage is discharged after the full reaction.

[0011] Fe(III) oxides drive dissimilatory iron reduction (DIR) by iron-reducing bacteria (IRB), which use extracellular Fe(III) as an electron acceptor to oxidize organic matter and simultaneously reduce Fe(III) to Fe(II). Feammox uses Fe(III) as an electron acceptor to oxidize ammonia nitrogen to N2 and NO2 - 、NO3 - ; Nitrate-dependent ferrous oxidation (NDFO) uses ferrous iron as an electron donor to reduce NO3 − N2, NO2 - NH4 + . Some products of the two processes of NDFO and Feammox are reactants with each other. The effective coupling of these two processes can effectively and synchronously remove nitrate and ammonia nitrogen, achieve deep denitrification, and help the oxidation of ferrous iron in NDFO and the reduction of ferric iron in Feammox to form an internal Fe(III) / Fe(II) cycle, thereby reducing the amount of iron salt added. Excessive organic matter will weaken the denitrification effect of Feammox. After the organic matter in the sewage is effectively removed by the front-end heterotrophic iron reduction process, favorable autotrophic conditions are created for the subsequent denitrification process. The carbon dioxide generated by the heterotrophic iron reduction process and Fe(II) can form ferrous carbonate precipitation, reduce greenhouse gas emissions, and achieve carbon dioxide fixation; the iron salts in the three processes can all achieve effective removal of phosphates. The biological treatment process for domestic sewage provided by the present invention can provide a low-carbon, low-material consumption solution for domestic sewage treatment through the coupling of the above processes, and the COD removal rate can reach more than 95%, and the ammonia nitrogen and phosphate removal rates can reach more than 90%.

[0012] The biological treatment process for domestic sewage provided by the present invention utilizes the principle of removing three pollutants in sewage by iron in different valence states, realizes the microbial driven iron redox mediated dissimilatory iron reduction, Feammox and NDFO to achieve the removal of carbon and nitrogen in sewage, and utilizes the generated Fe(II) to fix carbon dioxide, reduce greenhouse gas emissions, and utilizes the adsorption and crystallization between iron salts and phosphates to remove phosphorus in sewage. The C / N ratio in rural sewage is about 5-8, which will inhibit the effect of autotrophic denitrification technology. Therefore, at the front end, dissimilatory iron reducing microorganisms and a large amount of iron source are used to efficiently remove organic matter in sewage through dissimilatory iron reduction. After reducing the C / N, the sewage enters the Feammox pool, and the NH4 + N2 is generated by the Feammox process, and Fe(III) is reduced to Fe(II); NO3 is a partial product of Feammox - It can react with the remaining organic matter in the sewage to generate N2 through heterotrophic denitrification. At the same time, the Fe(Ⅱ) generated by Feammox can also react with NO3 - N generation through NDFO 2， Achieve deep nitrogen removal and realize Fe(Ⅱ) / Fe(Ⅲ) cycle through NDFO action.

[0013] Furthermore, in step S1, the iron source is iron ore or iron-containing waste sludge, and the dosage is 5-15 mmol / L; in step S2, the iron source is ferrihydrite, and the dosage is 5-15 mmol / L.

[0014] Preferably, the main pollutants in the domestic sewage in step S1 include organic matter, NH4 + and PO4 3- , pH is 6~8.

[0015] Furthermore, in step S1, the hydraulic retention time of domestic sewage in the dissimilatory iron reduction reaction tank is 6 to 20 hours, the effluent C / N ratio is <2, and the COD is below 80 mg / L; in step S2, the hydraulic retention time of domestic sewage in the iron ammonia oxidation reaction tank is 6 to 20 hours.

[0016] Furthermore, the Fe content in the reaction tank is regularly monitored. 2+ concentration, when Fe 2+ When the concentration exceeds 60%, intermittent aeration oxidation of Fe 2+ , reduce the addition of exogenous iron to achieve the iron oxidation cycle; or discharge the wastewater from the alienated iron reduction tank and realize the iron oxidation cycle by increasing the contact area between the top of the reaction tank and the air.

[0017] Furthermore, the Fe content in the reaction tank is regularly monitored. 2+ concentration, when Fe 2+When the concentration exceeds 60%, adjust the continuous flow mode to batch operation, start stirring to allow the sludge to contact with air to oxidize Fe 2+ After the end, turn off the stirring, let it stand and settle to drain the water, and switch to continuous flow mode.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects: (1) The present invention is suitable for domestic sewage treatment, with a simple treatment process and low cost. The technology of dissimilatory iron reduction, iron autotrophic ammonia oxidation and iron autotrophic denitrification is coupled to achieve the simultaneous removal of organic matter, nitrogen and phosphorus in sewage.

[0019] (2) The organic matter in sewage can be efficiently removed through the dissimilatory iron reduction technology, providing suitable conditions for the application of Feammox in actual sewage treatment.

[0020] (2) By strengthening the subsequent denitrification process through dissimilatory iron reduction, the autotrophic denitrification technology can be fully applied to actual sewage treatment, reducing or even eliminating the inhibitory effect of organic matter, creating the best environment for the autotrophic denitrification technology, and ensuring the efficient denitrification of Feammox.

[0021] (3) The autotrophic technology does not require additional aeration during the ammonia oxidation stage, and the generated nitrate does not require an external carbon source. At the same time, the added iron salt can be recycled. The subsequent autotrophic denitrification process does not need to consider sludge treatment and disposal, which is conducive to reducing treatment costs.

[0022] (4) The iron added to the heterotrophic iron reduction tank releases Fe(III) from the added iron source, and the Fe(III) is regenerated through rapid oxidation by air, reducing cost consumption while ensuring long-term and efficient removal of pollutants. At the same time, the generated CO2 can be fixed by Fe(II) to form FeCO3 precipitation, which can reduce greenhouse gas emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of the domestic sewage biological treatment system provided by the present invention.

[0024] In the figure: 1-water inlet tank; 2-peristaltic pump; 3-dissimilatory iron reduction reaction tank; 4-sludge; 5-iron source addition port; 6-mechanical stirring; 7-outlet weir; 8-iron ammonia oxidation reaction tank.

[0025] Figure 2 It is a schematic diagram of the principle of the present invention. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is described clearly and completely below in conjunction with the accompanying drawings of the specification. Obviously, the described implementation is only a part of the implementation of the present invention, not all of the implementations. Based on the implementation of the present invention, all other implementations obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example 1

[0027] A biological treatment system for domestic sewage based on iron drive, such as Figure 1 As shown, it includes a water inlet tank 1 and two reaction tanks connected in sequence by pipelines, the two reaction tanks are respectively a dissimilatory iron reduction reaction tank 3 and an iron ammonia oxidation reaction tank 8, and a peristaltic pump 2 is arranged between the water inlet tank 1 and the dissimilatory iron reduction tank 3. Both reaction tanks are provided with an iron source addition port 5 and an outlet weir 7, sludge 4 containing iron-reducing bacteria is inoculated in the dissimilatory iron reduction reaction tank 3, and sludge with iron ammonia oxidation function is filled in the iron ammonia oxidation reaction tank, and the iron ammonia oxidation reaction tank 8 is provided with a mechanical stirrer 6. Example 2

[0028] The process of treating domestic sewage using the system of Example 1 is as follows: Figure 2 As shown, the following steps are included.

[0029] (1) Preparation of simulated wastewater: Prepared with tap water, added with CH3COONa, NH4Cl and KH2PO4, and adjusted the influent pH between 6 and 8 with 1 M HCL and NaOH. Control the influent COD to 300 mg / L; NH4 + 50 mg / L, PO4 3- 5 mg / L.

[0030] (2) Anaerobic iron-containing sludge was inoculated in the dissimilatory iron reduction tank, and iron ore was filled at the bottom of the reactor; in the iron ammonia oxidation reaction tank, anaerobic ammonium oxidation granular sludge was used to domesticate the microorganisms required for the iron ammonia oxidation process, and 10 mM prepared ferrihydrite was added. The volume ratio of the dissimilatory iron reduction tank to the iron ammonia oxidation reaction tank was 1:11.

[0031] (3) The HRT of the dissimilatory iron reduction tank is set to 18 h, and the HRT of the iron ammonia oxidation tank is set to 18. The upflow reactor is adopted, and the sewage flows in from the bottom. There is an overflow weir on the top, and after flowing out, it enters the bottom of the next-level reaction tank to complete the reaction. At the same time, the upflow reactor reduces the subsequent sedimentation stage of the effluent, and no additional construction cost is required.

[0032] (4) After the sewage enters the dissimilatory iron reduction pool, the iron ore added to the pool will slowly release a large amount of Fe(III), providing sufficient substrate for the dissimilatory iron reduction process. The organic matter is rapidly consumed, causing the C / N ratio in the sewage to drop below 2. The Fe(II) generated at the same time can not only fix the generated CO2, reducing greenhouse gas emissions, but also participate in the crystallization process of phosphate to form phosphate minerals, such as blue iron stone, to achieve phosphorus recovery. Fe(III) can also achieve phosphorus adsorption. The dissolved oxygen in the sewage will also be completely consumed in this area, creating a more anaerobic environment for the subsequent process.

[0033] (5) After the C / N ratio of the effluent from the dissimilatory iron reduction tank decreases, the wastewater enters the iron-ammonia oxidation reaction tank. Through the action of Feammox, NH4 + Oxidized to N2, while producing a small amount of NO3 – Product, Fe(Ⅲ) is reduced to Fe(Ⅱ). The remaining organic matter and the generated Fe(Ⅱ) remove NO3 – This product realizes the cycle of Fe(Ⅱ) / Fe(Ⅲ) and consumes the remaining organic matter. The Fe(Ⅲ) in the iron ammonia oxidation reaction tank can also participate in the dissimilatory iron reduction process, so the organic matter in the sewage is further removed in this reaction tank. Phosphate is also further removed in this area through the combined action of adsorption and crystallization.

[0034] (6) Regularly monitor the iron concentration of the sludge in the two areas. When the Fe(II) concentration in the dissimilatory iron reduction reaction pool exceeds 60%, intermittent aeration can be used to oxidize Fe(II) to reduce the addition of exogenous iron and realize the iron oxidation cycle; or the sewage in the dissimilatory iron reduction pool can be discharged to increase the contact area between the top of the reaction pool and the air to realize the iron oxidation cycle. When the Fe(II) concentration in the iron-ammonia oxidation reaction pool exceeds 60%, the continuous flow can be changed to intermittent operation, and stirring can be turned on to allow the sludge to contact with the air to oxidize Fe(II); after the end, the stirring can be turned off, the sludge can be allowed to settle and the water can be discharged, and the operation can be changed to continuous flow mode.

[0035] (7) By running the Feammox reaction at a low C / N ratio, a small amount of iron is lost in the effluent. If the denitrification effect is still reduced after adjusting the operating mode according to (6), an appropriate amount of Fe(OH)3 can be added to improve the denitrification effect.

[0036] After stable operation, the effluent COD of the iron-ammonia oxidation reaction pool is below 10 mg / L, and NH4 + Below 5mg / L, PO4 3- Below 0.5mg / L.

[0037] Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention. The protection scope of the present invention is defined by the claims and their equivalent technical solutions.

Claims

1. A biological treatment system for domestic sewage based on iron drive, It is characterized in that The method comprises a water inlet tank and two reaction tanks which are connected in sequence by pipelines. The two reaction tanks are a dissimilatory iron reduction reaction tank and an iron ammonia oxidation reaction tank in sequence. Both reaction tanks are provided with an iron source addition port, a water inlet and an outlet weir. The dissimilatory iron reduction reaction tank is filled with sludge with iron reduction function, and the iron ammonia oxidation reaction tank is filled with sludge with iron ammonia oxidation function.

2. The biological sewage treatment system according to claim 1, It is characterized in that The dissimilatory iron reduction reaction tank is provided with an aeration device, and the iron ammonia oxidation reaction tank is provided with a stirring device.

3. The biological sewage treatment system according to claim 1, It is characterized in that If the C / N ratio in the effluent from the heterotrophic iron reduction reaction tank is >2, add a heterotrophic iron reduction tank.

4. The biological sewage treatment system according to claim 1, It is characterized in that If the effluent NH 4 + -N>5 mg / L, add an iron-ammonia oxidation reaction tank.

5. A process for treating domestic sewage by the domestic sewage biological treatment system according to any one of claims 1 to 4, It is characterized in that The following steps are involved: S1: Add sludge with iron reduction function into the dissimilatory iron reduction tank, fill it with iron source, introduce domestic sewage, start the dissimilatory iron reduction process and fully react; S2 fills the sludge with iron ammonia oxidation function into the iron ammonia oxidation reaction tank, adds the iron source, and the effluent from the dissimilatory iron reduction tank enters the iron ammonia oxidation reaction tank. After the iron ammonia oxidation process is started and fully reacted, the treated domestic sewage is discharged after the full reaction.

6. The process according to claim 5, It is characterized in that In step S1, the iron source is iron ore or iron-containing waste sludge, and the dosage is 5-15 mmol / L; in step S2, the iron source is ferrihydrite, and the dosage is 5-15 mmol / L.

7. The process according to claim 5, It is characterized in that The main pollutants of domestic sewage in step S1 include organic matter, NH 4 + and PO 4 3- , pH is 6 ~ 8.

8. The process according to claim 5, It is characterized in that In step S1, the hydraulic retention time of domestic sewage in the dissimilatory iron reduction reaction tank is 6 to 20 hours, the effluent C / N ratio is <2, and the COD is below 80 mg / L; in step S2, the hydraulic retention time of domestic sewage in the iron ammonia oxidation reaction tank is 6 to 20 hours.

9. The process according to claim 5, It is characterized in that Regularly monitor the Fe content in the reaction tank 2+ concentration, when Fe 2+ When the concentration exceeds 60%, intermittent aeration oxidation of Fe 2+ , reduce the addition of exogenous iron and realize the iron oxidation cycle.

10. The process according to claim 5, It is characterized in that Regularly monitor the Fe content in the reaction tank 2+ concentration, when Fe 2+ When the concentration exceeds 60%, the wastewater from the alienated iron reduction tank will be discharged, and the iron oxidation cycle will be realized by increasing the contact area between the top of the reaction tank and the air.

11. The process according to claim 5, It is characterized in that Regularly monitor the Fe content in the reaction tank 2+ concentration, when Fe 2+ When the concentration exceeds 60%, adjust the continuous flow mode to batch operation, start stirring to allow the sludge to contact with air to oxidize Fe 2+ After the end, turn off the stirring, let it stand and settle to drain the water, and switch to continuous flow mode.

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